Removing 0s from start and end - JavaScript

We are required to write a JavaScript function that takes in a number as a string and returns a new number string with all the leading and trailing 0s removed.

For example: If the input is ?

const strNum = '054954000'

Then the output should be ?

const output = '54954'

Using substring() Method

This approach uses two pointers to find the first non-zero character from the start and end, then extracts the substring between them.

const strNum = '054954000';

const removeZero = (str = '') => {
    let startLen = 0, endLen = str.length - 1;
    
    // Find first non-zero character from start
    while(str[startLen] === '0') {
        startLen++;
    }
    
    // Find first non-zero character from end
    while(str[endLen] === '0') {
        endLen--;
    }
    
    return str.substring(startLen, endLen + 1);
};

console.log(removeZero(strNum));
console.log(removeZero('00012300'));
console.log(removeZero('000'));

54954
123
0

Using Regular Expressions

A more concise approach using regex to match leading and trailing zeros.

const removeZeroRegex = (str) => {
    // Remove leading zeros, then trailing zeros
    return str.replace(/^0+/, '').replace(/0+$/, '') || '0';
};

console.log(removeZeroRegex('054954000'));
console.log(removeZeroRegex('00012300'));
console.log(removeZeroRegex('000'));

54954
123
0

Using parseInt() and toString()

Converting to number automatically removes leading zeros, then back to string removes trailing zeros from decimal representations.

const removeZeroNumber = (str) => {
    const num = parseInt(str, 10);
    return num.toString();
};

console.log(removeZeroNumber('054954000'));
console.log(removeZeroNumber('00012300'));
console.log(removeZeroNumber('000'));

54954
12300
0

Comparison

Edge Cases

Handle special cases like strings containing only zeros:

const removeZeroSafe = (str) => {
    let result = str.replace(/^0+/, '').replace(/0+$/, '');
    return result === '' ? '0' : result;
};

console.log(removeZeroSafe('000'));
console.log(removeZeroSafe('0'));
console.log(removeZeroSafe('102030'));

0
0
10203

Conclusion

The regex approach offers the cleanest solution for removing both leading and trailing zeros. Use parseInt() only when trailing zeros don't need to be preserved.